The call came Jan. 6, shortly after noon. Ellie Dehn had just rolled out of bed in the New York apartment she considers home — at least for the three months of the year she lives there.

She saw her agent’s name flash on her cell phone and picked up.

“I didn’t think it was anything special,” she said. “I thought he might be checking up on how it’s going in general.”

Instead, he had two questions: “Is Mimi memorized? How well do you know it?”

Mimi is the heroine of “La Bohème,” a role that Dehn, a soprano, has been preparing to debut in March at the Minnesota Opera.

“I said it’s probably 60, 70, 80 percent memorized, ’cause it kind of was. I knew it, but I had never tried it. And then I was like… Why?”

He broke the news: Anja Harteros bowed out of the San Diego Opera’s upcoming production due to a personal situation. The first performance was Jan. 30. Ian Campbell, the opera’s general director, wanted to cast Dehn as Mimi, alongside tenor Piotr Beczala as Rodolfo. Oh, and by the way, rehearsals were starting in five days. Was she up for it?

First reaction: “Oh my God, really!? Like they like me? They really like me? Kind of flattering!”

Second reaction: Terror. Because while any professional might get heart palpitations at the thought of a major deadline being pushed up a month, few have to deliver the final product in front of thousands of people.

A lyric soprano whose voice was called “radiant, colorful” by one reviewer and “combining metallic clarity and sensual richness” by another, Dehn is singing in San Diego for the first time. Her rise has been rapid. After graduating from Oberlin College in 2002 and attending graduate school at the Academy of Vocal Arts in Philadelphia, in 2007 she made her debut with the Metropolitan Opera singing Marguerite in “Faust” and returned to sing Mrs. Naidoo in Philip Glass’ “Satyagraha.” Future engagements include Teatro alla Scala, the Houston Grand Opera, Santa Fe Opera and, coming up this spring, the role of Freia in “Das Rheingold” with the Los Angeles Opera.

By the way, she’s not yet 30.

After her agent’s phone call, Dehn, took an hour to ask herself whether she was truly capable of pulling it together so quickly. She also asked a few voice coaches if they could fit her in for a cram session. They agreed, and the scramble began: memorizing lines and getting into a Puccini state of mind.

Days later, she was on a rehearsal stage in San Diego, trembling and coughing. Rather, the feeble Mimi was trembling. Dehn was all smiles.

“Thank God I knew a little more than I thought I did,” she said in an interview at the opera’s offices, nibbling on a salad between rehearsals. “It was kind of good to see what you can do when you have the pressure.”

She credits her success to luck.

“There are so many people that are really talented. There are so many people that have more beautiful voices than me or are better actresses. I am very aware I am very lucky,” she said.

But according to Campbell, there is a lot more to Dehn than she lets on. He sees in Dehn the consummate combination of voice, charisma, and looks: the opera trifecta.

“She is perfect for the role in every way,” Campbell said in an e-mail message. In 2007 he had auditioned Dehn, which is typical for singers who are just starting out, and he describes deciding to cast her now in this way: “I turned to my box of audition cards which includes new voices I have heard in performance. I got as far as the D’s when Ellie Dehn’s card popped up. I went no further.”

Those qualities may liken Dehn to a soprano she considers one of her idols, Renata Scotto.

“Mimi was one of her signature roles. She had a stunningly beautiful voice, but she also brings so much character to the words. Complete music and words and acting. It comes through even on a CD,” Dehn gushed, adding that she has trained with Scotto. “She’s the complete artist.”

Singing Mimi marks a shift in Dehn’s repertoire, since until now her voice has led her to specialize in Mozart. This is the first time she is singing a part that pulls her lower, into the most overtly expressive possibilities of Puccini. “Mozart is more of a structured line, whereas with Puccini you have a lot of freedom to blossom,” she explained. “Because I am getting older, it was the time to see how it felt. It was kind of a pleasant surprise, because it’s comfortable. If I had tried to sing it in college it would have felt totally wrong.”

Raised on classical and choral music (Dehn’s grandfather was a flutist), she came around to opera in college, where it was all the rage.

“All my friends really loved opera,” she said. “Since all my peers were really excited about it, I also ended up diving into it. Then it becomes kind of like a drug. It’s not enough. You want to find out more about this composer, that composer, different singers, the contemporary ones, the ones from the past.”

One of her goals is to make opera attractive to people in her generation. She pronounces that its plots are better than movies and is gleeful when friends come to watch her performances and like what they see.

“I did ‘Romeo and Juliet’ at Minnesota Opera a couple of years ago. I had some friends come and they really liked it, and ‘Romeo and Juliet’ is like three and a half hours long, so for them to like it was really cool,” she said.

Now here’s the thing you need to know about Dehn. She may be lucky (or merely very talented), she may have the voice and looks of a leading lady, but she is also disciplined and hard working. She does yoga three times per week and didn’t waste a moment after arriving in San Diego to ask about studios in town. When the salad she ordered for lunch came with a crusty baguette, she said it looks delectable—but left the bread untouched.

She applies that same focus when she prepares for roles. To memorize lines, she uses a method a friend from graduate school taught her during a study session at Starbucks: write the words, over and over and over. She opened a notebook that was densely packed with frenzied script in Italian, to illustrate.

“You can visualize the words,” she said. “It really works.”

The next step is “coach the heck out of it.” She works with several teachers, because more ideas are better than one.

That drive and determination, though, are tempered by a carefree attitude, which helps keep her sane under pressure.

When she plays tour guide in New York to family from Minnesota, where she grew up, she skips the clichéd haunts and takes them to do average New Yorker things — getting eyebrows threaded or picking up a slice from a divey pizza joint in her neighborhood.

“People call me a hippie,” she said. “I don’t, like, dress up a lot all the time. I like to be comfortable and not get so stressed out about little things. Have a sense of humor. There is that stigma about the diva — everything has to be a certain way,” she said, suggesting she views herself differently.

Her apartment is decorated in a mix of styles — “I guess it’s kind of bohemian,” Dehn summarized — though lately she’s been trying to declutter. How’s that for a fitting parallel with the role she’s about to sing. Here’s one more: Dehn used to work as a florist, and Mimi is a flower maker. But the similarities stop there. Opera usually ends in tragedy, and Dehn is poised for triumph.